Octave PHONO MODULE Owner's Manual page 23

8.2. Technical data, diagrams
Why utilize a balanced input for MC systems?
Magnetic stray fields are always present in a room due to the mains cables and the power transform-
ers of the components. The stray field induces hum and noise in the cartridge and the phono cable.
If there is a hum in such a system, one has no means to minimize the level of the hum other than to
possibly change the location of the turntable.
In contrast to common opinion, mains and transformer stray fields are not limited to only 50 Hz. The
graph below depicts three different stray fields. First ( 1 ) the stray field of a room without transformer,
the stay field of the shielded transformer of the Octave Phono Module ( 2 ), and the stray field of a
conventional transformer ( 3 ). It is easy to see that the stray field extends to the midrange (with
peaks up to 2 kHz). This causes interference with the signal of the MC pickup. A balanced input
effectively reduces the hum and the interference. To ensure optimum sound quality and reproduction,
the balanced connection is most effective, especially when the cable length and the placement of
the turntable cannot be changed.
The Common Mode Rejection Ratio of the Balaced Input is shown in Diagram 2, the CMMR reaches
100 dB / 50 Hz, meaning a stray pick up can theoretically be reduced by a factor of 100,000.
1. Strayfield Graph of different Mains Transformers
2. Common Mode Rejection Ratio MC XLR- Input
8. TECHNICAL DATA
25
Top Graph (3):
Strayfield of a conven-
tional Transformer.
Middle Graph (2):
Strayfield of the Phono
Module Transformer.
Lower Graph (1):
Strayfield in a room with-
.
out a Transformer
Status: April 2020